Full dynamics of a red blood cell in shear flow

At the cellular scale, blood fluidity and mass transport depend on the dynamics of red blood cells in blood flow, specifically on their deformation and orientation. These dynamics are governed by cellular rheological properties, such as internal viscosity and cytoskeleton elasticity. In diseases in which cell rheology is altered genetically or by parasitic invasion or by changes in the microenvironment, blood flow may be severely impaired. The nonlinear interplay between cell rheology and flow may generate complex dynamics, which remain largely unexplored experimentally. Under simple shear flow, only two motions, “tumbling” and “tank-treading,” have been described experimentally and relate to cell mechanics. Here, we elucidate the full dynamics of red blood cells in shear flow by coupling two videomicroscopy approaches providing multidirectional pictures of cells, and we analyze the mechanical origin of the observed dynamics. We show that contrary to common belief, when red blood cells flip into the flow, their orientation is determined by the shear rate. We discuss the “rolling” motion, similar to a rolling wheel. This motion, which permits the cells to avoid energetically costly deformations, is a true signature of the cytoskeleton elasticity. We highlight a hysteresis cycle and two transient dynamics driven by the shear rate: an intermittent regime during the “tank-treading-to-flipping” transition and a Frisbee-like “spinning” regime during the “rolling-to-tank-treading” transition. Finally, we reveal that the biconcave red cell shape is highly stable under moderate shear stresses, and we interpret this result in terms of stress-free shape and elastic buckling.     

Hepatorenal Syndrome: Are We Missing Some Prognostic Factors?

Background  

Hepatorenal syndrome (HRS) is the functional renal failure associated with advanced cirrhosis and has also been described in fulminant hepatic failure. Without liver transplantation its prognosis is dismal. Our study included patients with type 1 HRS associated with cirrhosis, who were not liver transplant candidates.     

Effect of ozone on periodontopathogenic species—an in vitro study

The in vitro study was aimed to determine the effect of ozone on periodontopathogenic microorganisms. Ozone was generated for 6 s–2 × 24 s (corresponding to 0.56 mg–2 × 2.24 mg of ozone) against 23 mainly anaerobic periodontopathogenic species. Agar diffusion test was used as a screening method. Then, the killing activity was tested in a serum-free environment and with 25% v/v inactivated serum. Further, the effect of ozone on bactericidal activity of native serum was analyzed against Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans. Agar diffusion test showed a high efficacy of ozone against microorganisms, especially against Porphyromonas gingivalis. This result was confirmed by the killing tests; most of the strains in a concentration of 10⁵ were completely eliminated after twofold 18-s application of ozone. Only four of the six potentially “superinfecting” species (Staphylococcus aureus, Enterococcus faecalis, Enterobacter cloacae, Candida albicans) survived in part. Addition of heat-inactivated serum reduced the killing rate of ozone by 78% after 6-s and by 47% after twofold 18-s exposures; no strain was completely eradicated after any application of ozone. The bactericidal effect of native serum was enhanced after application of ozone; no effect was visible on the included A. actinomycetemcomitans strain which was found to be completely resistant to the bactericidal action of serum. In conclusion, (a) ozone has a strong antibacterial activity against putative periodontopathogenic microorganisms, and (b) the bactericidal effect is reduced in the presence of serum. Ozone may have potential as an adjunctive application to mechanical treatment in periodontitis patients.     

The time-averaged inflammatory disease activity estimates the progression of erosions in MRI of the sacroiliac joints in ankylosing spondylitis

A method to estimate the individual ankylosing spondylitis (AS) patient radiological progression of semi-quantitative magnetic resonance imaging (MRI) changes in the sacroiliac joints has not been described yet, which this study examines. Inflammatory disease activity and MRIs of the sacroiliac joints of 38 patients with recent onset established AS were analyzed at baseline and during follow-up. Sacroiliac MRIs were semi-quantitatively assessed using a modification of the "Spondylarthritis Research Consortium of Canada" (SPARCC) method. In each patient, the annual inflammatory disease activity was estimated by the time-averaged C-reactive protein (CRP; mg/l), calculated as the area under the curve. The mean (SD) CRP decreased from 1.3 (1.8) at baseline to 0.5 (0.6) at follow-up MRI (p < 0.04), which has been performed after a mean (SD) disease course of 2.8 (1.5) years. The mean (SD) annual increase (?) of SPARCC score from baseline to follow-up MRI was 0.4 (0.4). Baseline individual SPARCC sub-score for bone marrow edema did not statistically significantly correlate with individual ?SPARCC sub-score for erosions (p = N.S.). The individual AS patient correlation between annual time-averaged inflammatory disease activity and each annual ?SPARCC sub-scores was only statistically significant for erosions (p < 0.01; r = 0.71). Our results show that bone marrow edema and contrast-medium enhancement at baseline do not relate to the progression of erosions but the calculation of the individual patient annual time-averaged inflammatory disease activity allows to estimate the annual progression of erosions in sacroiliac MRIs of patients with AS.